The present invention relates to a magnetic head for magnetically high-density recording of information on a magnetic recording medium such as a magnetic tape and a method of easily manufacturing the same.
As a recording medium for high-density recording is used a high-coercive medium such as metal tape and as a magnetic head for the high-coercive medium is known a so-called metal-in-gap head (which will be referred to as MIG head). The MIG head comprises first and second core halves each made of a ferrite and held in abutment against each other so as to form a magnetic gap and further includes a magnetic metal material with a high saturation magnetization which is provided only in the vicinity of the magnetic gap. The MIG head shows an excellent recording characteristic because of generation of a strong recording magnetic field from the magnetic metal material during recording and has an excellent reproduction characteristic up to a high-frequency region during reproduction since most of the magnetic path is composed of a ferrite with a small eddy current loss.
Generally, in manufacturing of the MIG head, the magnetic metal material is adhered from the gap surface side of a magnetic core half by means of the sputtering, deposition or the like. The thickness of this magnetic metal material to be adhered is required to be below a predetermined value by taking into account the difference in coefficient of thermal expansion between the magnetic metal material and the ferrite core, degree of the eddy current loss in the magnetic metal material, forming speed of the magnetic metal material, for example.
Generally, when a joint portion between the magnetic metal and the ferrite portion exists in the tape-contact surface of the MIG head, the joint portion between different kinds of magnetic materials is known to act as a pseudo gap resulting in generation of noises. One current method for resolution of this problem involves arranging the joint portion so as not to be parallel to the magnetic gap.
On the other hand, in conventional MIG heads, various problems take place because the magnetic metal material in the vicinity of the magnetic gap is adhered from the gap surface sides of the ferrite core halves thereto by means of the sputtering or the like.
First, the machining, necessary for the removal of affection of noises due to the pseudo gap, is troublesome. That is, for the non-parallel arrangement, the adhesion of the magnetic metal material may be effected, for example, so that the joint portion is obliquely formed with respect to the magnetic gap or formed in zigzags. In these cases, the grinding of the gap surface should be made taking into account the track width, the thickness of the adhered magnetic metal material and so on, thereby resulting in being troublesome in machining.
In the second place, the magnetic metal material is subject to be attached to the back gap of the magnetic head because of adhesion of the magnetic metal material from the gap surface side. With the attachment of the magnetic metal material to the back gap portion, the eddy current loss is particularly increased at only the attached portion so as to lower the reproduction efficiency. Therefore, it is required to remove the magnetic metal material attached to the back gap portion, thereby resulting in increase in machining steps.
The third place is that the thickness of the magnetic metal material to be attached is required to be below a predetermined value whereby the ferrite portion is presented relatively near the magnetic gap and further comes into contact with the track of the recording medium. Generally, the magnetic head starts to come into contact with a magnetic tape with respect to the magnetic gap, and in the conventional MIG heads in which the ferrite portion is positioned near the magnetic gap, since the ferrite portion comes into contact with the magnetic tape even in the case that the contact area between the head and magnetic tape is small, noises tend to be generated due to the sliding movement of the magnetic tape on the head in reproduction. In addition, when the ferrite portion exists within a portion of the tape-contact surface of the head corresponding to the width of a track of the magnetic tape, in recording or reproduction, it has been confirmed that the ferrite portion can produce wide-band modulation noises. Therefore, it is preferable that on the tape-contact surface the ferrite portion extending in the direction perpendicular to the head moving direction does not exist in the vicinity of the magnetic gap.
In the fourth place, in the case of using a magnetic tape which produces a partial abrasion between the magnetic metal material and the ferrite portion even by a slight amount, the MIG head may generate specific noises. This is considered to be due to generation of beating of the magnetic tape in the vicinity of the joint portion because the joint portion between the magnetic metal material and the ferrite portion on the tape-contact surface of the head is presented so as to cross the head-moving direction, and in recording/reproducing noises appear in the vicinity of the carrier frequency in the reproduction spectrum.
For eliminating the above-described problems have been proposed various methods in which the adhesion of the magnetic metal material to the ferrite core is performed from the tape-contact surface side by means of the sputtering or deposition so as not to put a adhesion layer therebetween (for example, as disclosed in Japanese patent provisional publication Nos. 55-42380, 62-33308). However, in these methods, the manufacturing and track-width limiting results in being troublesome and hence actually difficult to provide a MIG head with a structure which provides an excellent electro-magnetic conversion characteristic and allows mass production.